The objective of the proposed program is the development of an improved mammary prosthesis significantly less prone to the major complication of devices currently used caused by the formation of a thickened fibrous tissue capsule around the implant. The basic approach is to alter the surface morphology of the implant from smooth silicone rubber to a textured surface which promotes tissue adhesion and attachment. This surface will be generated by extruding silicone rubber fibrils and forming them into a matrix bonded to the exterior of the implant. Based on experience with implantable compliance chambers for artificial heart systems, surface morphology was shown to be a major determinant of tissue capsule thickness formed around those devices. Test specimens of smooth silicone rubber, a textured surface previously characterized, and the textured silicone rubber will be evaluated in vivo for tissue capsule thickness and composition histologically. Other uses for the technology developed include improved compliance chamber systems, cardiac pacemaker casings, implantable polymeric drug delivery systems, or any application in which excessive scar tissue formation can cause undesirable symptoms or interfere with the performance of the device.